Chronic wasting disease (CWD) of deer and elk is an emerging highly transmissible prion disease now recognized in 18 States, 2 Canadian provinces, and Korea. We have shown that Infected deer harbor and shed high levels of infectious prions in saliva, blood, urine, and feces, and in the tissues generating those body fluids and excreta, thereby leading to facile transmission by direct contact and environmental contamination. We have also shown that CWD can infect some non-cervid species, thus the potential risk CWD represents to domestic animal species and to humans remains unknown. Whether prions borne in blood, saliva, nasal fluids, milk, or excreta are generated or modified in the proximate peripheral tissue sites, may differ in subtle ways from those generated in brain, or may be adapted for mucosal infection remain open questions. The increasing parallels in the pathogenesis between prion diseases and human neurodegenerative conditions, such as Alzheimer's and Parkinson's diseases, add relevance to CWD as a transmissible protein misfolding disease. The overall goal of this work is to elucidate the process of CWD prion transmission from mucosal secretory and excretory tissue sites by addressing these questions: (a) What are the kinetics and magnitude of CWD prion shedding post-exposure? (b) Are excreted prions biochemically distinct, or not, from those in the CNS? (c) Are peripheral epithelial or CNS tissues, or both, the source of excreted prions? and (d) Are excreted prions adapted for horizontal transmission via natural/trans-mucosal routes? The specific aims of this proposal are: (1) To determine the onset and consistency of CWD prion shedding in deer and cervidized mice; (2); To compare the biochemical and biophysical properties of excretory vs. CNS prions; (3) To determine the capacity of peripheral tissues to support replication of CWD prions; (4) To determine the protease- sensitive infectious fraction of excreted vs. CNS prions; and (5) To compare the mucosal infectivity of excretory vs. CNS prions. Understanding the mechanisms that enable efficient prion dissemination and shedding will help elucidate how horizontally transmissible prions evolve and succeed, and is the basis of this proposal. Understanding how infectious misfolded proteins (prions) are generated, trafficked, shed, and transmitted will aid in preventing, treating, and managing the risks associated with these agents and the diseases they cause.